An in depth look at
astrophotography has been left
to the dedicated section
Astrophotography. This section briefly
introduces why we use photography in Astronomy.

There are many important tools in Astronomy, but
nothing is more valuable than a camera - in the case
of the late 20th and beyond the
CCD is invaluable.
It all comes down to what our eyes can perceive. Our
eyes are great for day to day activity, but to
scrutinize faint object looking through a
telescope,
our eyes are the last choice. Our sensory retina is
just not designed for such tasks.

Gaseous appearance of nebula and
galaxies are
evident when viewing with the eye, but chances are
the image will be mono-chromatic - one color. The
larger the
telescope, the discerning a particular
object may be, but the vivid color is just not
there. All of the pretty Hubble images or images in
magazines of celestial objects are captured via long
period exposures.

There are basically two methods of photography
today:
film and
CCD.
Film based photography reigned
supreme in regards to field of view. The
CCD chips
in the early days covered may a few degrees of sky
at one time while plate
film covered as much as 14
degrees at one time. As
CCD's grew larger, cheaper,
and better,
CCD's have proven to be the workhorse
for
astrophotography. The reasons are simple:

CCD's (Charged Coupled Devices) are linear
in response - meaning that twice the exposure
means twice the signal;
film is not

There are no chemicals required

CCD image is ready almost immediately,
film
must be developed (and sometimes the image may
not be what was intended)

CCD's store numerical data so numerous data
analysis can be performed without damage to the
original;
film could be scanned, but that uses
pricey drum scanners